The alt attribute is for text that should be displayed if for some reason an image isn’t displayed (e.g. the user has images turned off). This text should describe the content of the image in a way that will help users who don’t see the image understand what it is for. If the image is just an interface graphic that doesn’t need text to describe its content (e.g. spacer.gif), leave the alt attribute empty like this: alt=”"

Use the title attribute to give extra information about the image, such as its title. You can in fact use the title attribute in this way for any HTML element, not just images. Think of it as a kind of elemental metadata.